1. Field of the Invention
The present invention relates to the field of digital circuits, and in particular to the area of energy consumption required by clock-gating.
2. Background
Complicated digital circuits typically comprise millions of transistors. Circuit designers typically utilize computer-added design programs to aid their design process. Once a designer has finished the conceptual design of a circuit, there are many optimizations which can be made.
For example, energy consumption of the digital circuit has become one of the critical factors in digital systems, because of the requirement to dissipate this energy in high-density circuits and to extend the battery life in portable systems such as devices with wireless communication capabilities. It is known in prior art that the clock circuitries are one of the most energy-consuming components in a digital circuit.
In “IEEE transactions on circuits and systems—II: Analog and digital signal processing, vol. 44, nr. 6, June 1997, page 507 to 516, “Individual flip-flops with gated clocks for low power data pasts”, Thomas Lang et al., a method for redesigning a digital circuit under the aspect of power saving is published, which discloses some techniques to reduce energy consumption by individually deactivating the clock, when flip-flops do not have to change their value. For selected digital circuits, such as a carry-save adder and an accumulator circuit, some improved flip-flop structures are proposed which were evaluated using energy models and which were validated by switch-level simulations.
Although significant energy reductions can be achieved by this prior art method for the selected circuit designs, this method cannot be used for any other circuits selected arbitrarily according to the actual need of a circuit designer, as the published method is only applicable for the concrete exemplary circuits described therein.
A second disadvantage is that the published method does not work fully automatically. So, a circuit designer is still required to have detailed knowledge of the circuit design, before he may apply the prior art method, or even apply only some general idea derivable from it.